Purpose: For proper preoperative planning of oral implants, the need has increased for tomographic imaging for precise determination of anatomic dimensions. However, concern for radiation exposure, which is substantial with computerized tomography (CT), has also grown. In the present study, the validity of jawbone width assessment and delineation by means of cone-beam CT (CBCT) and spiral tomography on dry mandibles was compared. Secondly, the subjective image quality of CBCT images with those obtained by multi-slice spiral CT (MSCT) of a fixed ex vivo cadaver with its soft tissues was compared. Materials and Methods: The study included 25 dry human mandibles for the dimensional study and 1 formalized maxilla for image quality assessment. Measurements of the mandibles by means of a digital sliding caliper acted as the gold standard. Radiographic examination of the premolar and canine regions was performed with both CBCT and spiral tomography. Observational measurements were carried out by postgraduates in oral imaging. Subjective image quality was assessed on the fixed maxilla, including soft tissues, by comparing CBCT and MSCT. Inter- and intraobserver variability were determined. Results: Direct mandibular measurements were on average 0.23 mm (SD 0.49) and 0.34 mm (SD 0.90) larger than the CBCT and spiral tomography measurements, respectively. Subjective image quality of the CBCT was significantly better than for the MSCT with regard to visualization and delineation of the lamina dura and periodontal ligament space. Subjective image quality of the MSCT was significantly better for the MSCT than the CBCT for the gingiva and cortical bone. Conclusions: These results indicate that on dry mandibles, jawbone width measurements by means of CBCT and spiral tomography are reliable, even if on average they slightly underestimate the bone width. For the subjective image quality, the CBCT offered better visualization of details of the small bony structures. Spiral tomography offered better visualization of the cortical bone and the gingiva.